Bone and Joint Infections

February 13, 2003 Cass Djurfors

Objectives:

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2.

Osteomyelitis Septic Arthritis     Epidemiology Clinical features Diagnosis Management

Epidemiology

Bimodal age distribution   Under 20 Over 50 Pediatrics:  boys>girls  Usually no identifiable risk factors Adults:  Usually have risk factors

Bone and Joint Infections: Mechanism

Hematogenous seeding most common Seeding from a contiguous source of infection Direct inoculation of the bone, from surgery, trauma or joint aspiration

Risk factors for bone and joint infections:

diabetes mellitus sickle cell disease AIDS alcoholism IV drug abuse chronic corticosteroid use preexisting joint disease other immunosuppressed states postsurgical patients—especially those with prosthetic devices

Pathogens:

Bacteria are most common Viruses, fungi and parasites are possible Staph aureus most common in all ages except neonates GBS most common in neonates H. influenzae b has essentially disappeared as a pathogen in vaccinated children

Pathogens:

Gonococcal arthritis is the most common type of septic arthritis in individuals under 30 years old In the elderly, gram-negative bacteria account for a higher percentage of cases of bone and joint infections than in younger people MRSA, MRSE, and VRE have emerged as a significant microbiologic problem in the past decade

Pathogens:

Usually unimicrobial Polymicrobial (36 to 50%) more likely in diabetic foot osteomyelitis, posttraumatic osteomyelitis, chronic osteomyelitis, and chronic septic arthritis

Osteomyelitis: Presentation

May be acute or chronic Pain over the affected bone In children: limp or refusal to weight Localized warmth, swelling, and erythema Fever is inconsistently present Systemic complaints often reported: headache, fatigue, malaise, and anorexia

Osteomyelitis: Presentation

Point tenderness over the infected segment Palpable warmth and soft-tissue swelling with erythema may be present

Osteomyelitis: Diagnosis

WBC is neither sensitive nor specific  Values commonly range from normal to 15,000/mm 3 ESR usually elevated  One series reported 90% sensitivity   Very nonspecific however Can be used to follow treatment CRP  yet another nonspecific marker of inflammation

Osteomyelitis: Diagnosis

Plain films:  Low sensitivity early in the disease       3-5 days: may detect soft tissue edema 7-10 days: >66% still have normal x-rays 30-50% of bone mineral must be lost to detect lucency on plain film By 28 days, >90% of plain films will be positive Characteristic finding: lucent lytic lesions of cortical bone destruction Advanced disease: lytic lesions are surrounded by dense, sclerotic bone, and sequestra may be noted

Plain radiograph of tibia. Lucent areas in metaphysis are sites of advanced osteomyelitis

Plain radiograph of humerus. Distal portion of humerus has involucrum formation, representing advanced case of osteomyelitis.

Osteomyelitis: Diagnosis

Bone Scan:     More useful early on than plain radiographs Can detect osteomyelitis within 48 to 72 hours of disease onset Sensitivity 90% with technetium-99 scan False positive rate as high as 64%  Trauma, surgery, tumours, soft tissue infection

Example of gallium technetium uptake. (top) (bottom) and bone scans in advanced osteomyelitis of tibial metaphysis. Both scans show increased radionuclide

Osteomyelitis: Diagnosis

111   In-labeled WBC scan Can distinguish infected bone from bone that has increased turnover from fractures, surgery, prostheses, osteoarthropathy, and tumor Usually reserved for situations of equivocal or normal bone scans in patients where osteomyelitis is still a consideration

Osteomyelitis: Diagnosis

CT  Used for infection in bones that are difficult to visualize on plain radiographs and bone scans: sternum, vertebrae, pelvic bones, and calcaneus    Appears as rarefaction, or lucent areas, on the CT scan images Gas may also be visible in bony abscess cavities Limitation: disease must be present for > 1 week

Osteomyelitis: Diagnosis

MRI   Good for early detection Limited availability

Osteomyelitis: Diagnosis

Microbiologic Diagnosis:    Needle aspiration or surgical specimen is best Swab of draining wound or sinus is not adequate Blood cultures in untreated patients are positive ~50% of the time

Differential Diagnosis:

Tumour:  Osteoid osteoma, chondroblastoma, Ewing’s sarcoma, metastases, lymphoma Trauma Myositis ossificans Erythema nodosum Cellulitis Eosinophilic granuloma

Osteomyelitis: Management

IV Antibiotics   Empiric broad spectrum initially Narrow appropriately when sensitivities available  4-6 weeks +/- Surgical debridement   Often not needed for acute hematogenous osteomyelitis in children Required in the diabetic foot or chronic osteomyelitis HBO  Controversial

Special considerations

Kids: usually acute hematogenous and often responds to Abx alone Vertebral osteomyelitis   Risk of paralysis!

Watch for epidural abscess  Careful with back pain and fever in IVDU Post-traumatic osteomyelitis:   10% of open fractures 2% with puncture wounds: Pseudomonas aeruginosa and S. aureus

Special considerations

Diabetic foot:    Usually chronic and polymicrobial Surgical debridement almost always required Amputation often required Sickle cell disease:   Increased risk of osteomyelitis S. aureus and Salmonella species

Empiric Therapy Adults: CHA

Osteomyelitis

Hematogenous IVDU Contiguous: vascular insufficiency, diabetic foot S. aureus P. aeruginosa Polymicrobial Nail-puncture of foot Post-op prosthetic joint

Pathogen

S. aureus P. aeruginosa S. aureus S. epidermidis

Therapy

Cloxacillin or Cefazolin +/- Gentamicin Cloxacillin or Cefazolin + Gentamicin Clinda + Cipro or Ancef + Metronidazole Severe: imipenem or pip tazo Prophylaxis: cipro Treatment:pip-tazo + tobramycin Vancomycin + Gentamicin

Empiric Therapy Kids: CHA

Osteomyelitis Pathogen Therapy

Neonates GBS, S. aureus, Enterobacteriaceae Cloxacillin + Cefotaxime Children Cloxacillin Sickle cell Post-op S. aureus, Strep, H. flu S. aureus, Salmonella sp.

S.aureus, GAS, Enterobacteriaceae Cloxacillin + Cefotaxime Cefazolin +/ Gentamicin Post-op spinal rods or sternotomy S. aureus, CNS, GAS, Enterobacteriaceae, Pseudomonas Vancomycin + Gentamicin Nail puncture of foot Pseudomonas aeruginosa Piperacillin+Tobra or Ceftazidime + Tobra

Disposition:

Inpatient Outpatient IV antibiotic therapy Outpatient PO antibiotic therapy (usually as step-down)

Septic Arthritis: Presentation

Usually hematogenous but may also result from contiguous spread or direct inoculation Occurs in all age groups Most common in children Usually monoarticular Polyarticular in less than 10% of pediatric cases and less than 20% of adult cases Hip and knee are most frequently affected

Septic Arthritis: Presentation

Predisposing factors:    Any joint disease  Osteoarthritis  Gout  Rheumatoid arthritis Surgery IVDU

Septic Arthritis: Presentation

Usually acute in onset Joint pain is main feature – worse with movement (careful with immunosuppressed and steroid dependent patients) Kids may refuse to use the affected limb Fever - 80% of children, > 40% of adults

Septic Arthritis: Presentation

Physical exam:  Joint is held in position of greatest comfort, slight flexion     Swelling, erythema, and warmth in almost all cases Palpation of the septic joint causes exquisite pain Both flexion and extension of the joint cause severe pain Effusion

Septic Arthritis: Diagnosis

Joint fluid for culture and analysis Knee joint is both the most likely to be infected and the easiest to aspirate in the ED Other joints (hip) may require ortho consultation +/- ultrasound or fluoroscopy guided aspiration Iatrogenic septic arthritis occurs in less than 1 in 10,000 joint injections or aspirations

Septic Arthritis: Diagnosis

Joint fluid:  aerobes, anaerobes and fungi    Gram stain Cell count and differential - wbc > 50000/mm 3 Glucose – decreased in septic arthritis with joint fluid/serum glucose ratio < 1:2. Synovial tissue from arthroscopy can be helpful in diagnosis

Septic Arthritis: Diagnosis

Blood cultures positive in 25% to 50% of cases ESR elevated in ~90% WBC may or may not be elevated Plain radiographs not very helpful except to reveal joint effusion Bone scan will be “hot” but causes unnecessary delay

Special Considerations:

Kids:   More common than osteomyelitis Of all cases in kiddies, 2/3 under age 2   Neonates: GBS, S. aureus, GNB >3 months: S. aureus > GAS > S. pneumo Teenagers and young adults:   N. gonorrhoeae Most are symptomatic with genital/oral infection   Classic triad of disseminated gonococcal infection is migratory polyarthritis, tenosynovitis, and dermatitis Joint fluid may be negative…treat on suspicion

Septic Arthritis: Differential

Kids       Osteomyelitis JRA Transient synovitis Legg-Calvé-Perthes disease Slipped capital femoral epiphysis Rheumatic fever

Septic Arthritis: Differential

Adults:  Osteomyelitis       Gout Pseudogout Reiter’s syndrome Psoriatic arthritis Arthritis associated with inflammatory bowel disease and ankylosing spondylitis Traumatic hemarthrosis

Septic Arthritis: Management

Orthopedic emergency Immediate IV Abx Needle vs. surgical decompression Abx alone in gonococcal arthritis only

Septic Arthritis: CHA Adults

Septic Arthritis

Adults (native joint +/- penetrating trauma) Gonococcal

Pathogen

S. aureus, P. aeruginosa N. gonorrhoeae

Antibiotics

Cloxacillin or cefazolin +/ gentamicin Cefotaxime Rheumatoid arthritis Prosthetic joint IVDU S. aureus, Strep sp, Enterobacteriaceae S. aureus, S. epidermidis, others S. aureus, P. aeruginosa Cefazolin +/ gentamicin Vancomycin + gentamicin Cloxacillin or cefazolin +/ gentamicin

Septic Arthritis: Kids

Septic Arthritis Pathogen Neonates GBS, S. aureus, Enterbacteriac eae Children S. aureus, Strep sp., rarely H. flu Sexually active N. gonorrhoeae Antibiotics Cloxacillin + Cefotaxime <5yrs: cefuroxime >5yrs:Cloxacilli n or cefazolin Cefotaxime

Septic Arthritis: Disposition

Diagnostic joint fluid aspirate or high clinical suspicion requires admission Non-diagnostic aspirates with equivocal clinical findings may be discharged home and re-evaluated in 24 hours Be conservative (consider admission) for patients with joint disease, prosthetic joints or immunosuppression and suspected septic arthritis